create table Test as
select '2010-12-01 00:01:00' 日時, 1 項目
union all select '2010-12-01 00:01:00', 1
union all select '2010-12-01 00:02:00', 1
union all select '2010-12-01 00:03:00', 2
union all select '2010-12-01 00:04:00', 2
union all select '2010-12-01 00:05:00', 2
union all select '2010-12-01 00:06:00', 3
union all select '2010-12-01 00:07:00', 3
union all select '2010-12-01 00:08:00', 0
union all select '2010-12-01 00:09:00', 0
union all select '2010-12-01 01:00:00', 4
union all select '2010-12-01 01:01:00', 4
union all select '2010-12-01 01:02:00', 5;

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

SELECT A.時間,A.項目,A.項目件数,A.最新日時
FROM (
  SELECT SUBSTR(日時, 12, 2) AS 時間, 項目,COUNT(項目) AS 項目件数,MAX(日時) AS 最新日時 
  FROM Test 
  WHERE 日時 BETWEEN '2010-12-01 00:00:00' AND '2010-12-01 23:59:59' 
  GROUP BY SUBSTR(日時, 12, 2),項目 
  ) AS A
  INNER JOIN (
    SELECT 時間,MAX(項目件数) AS 最大項目件数
    FROM (
      SELECT SUBSTR(日時, 12, 2) AS 時間,COUNT(項目) AS 項目件数
      FROM Test
      GROUP BY SUBSTR(日時, 12, 2),項目
      )
    GROUP BY 時間
    ) AS B
  ON (A.時間 = B.時間 AND A.項目件数 = B.最大項目件数)
  INNER JOIN (
    SELECT 時間,MAX(最新日時) AS 最新日時
    FROM (
      SELECT SUBSTR(日時, 12, 2) AS 時間,COUNT(項目) AS 項目件数,MAX(日時) AS 最新日時
      FROM Test
      GROUP BY SUBSTR(日時, 12, 2),項目
      )
    GROUP BY 時間,項目件数) AS C
  ON (A.時間 = C.時間 AND A.最新日時 = C.最新日時);